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Chapter 11 Growth I. Introduction A. Growth Defined

Chapter 11 Growth I. Introduction A. Growth Defined 1. Increase in mass due to the division and enlargement of cells 2. Types of growth in plants a. Determinate growth b. Indeterminate growth 3. Differentiation of cells

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Chapter 11 Growth I. Introduction A. Growth Defined

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  1. Chapter 11 Growth I. Introduction A. Growth Defined 1. Increase in mass due to the division and enlargement of cells 2. Types of growth in plants a. Determinate growth b. Indeterminate growth 3. Differentiation of cells B. Development Defined • the process of growth and differentiation of cells into tissues, organs, and organisms

  2. II. Plant Hormones A. Auxins 1. Early experiments by Darwin 2. Discovery of auxin by Frits Went (1926) 3. Characteristics of auxins a. Sites of production 1) Apical meristems 2) Buds 3) Young leaves 4) Other active young plant parts b. Polar movement • flow of auxins away from their source of synthesis

  3. 4. Naturally occurring auxins a. Indoleacetic acid (IAA) b. Phenylacetic acid (PAA) c. 4-chloro-indoleacetic acid (4-chloro-IAA) 5. Synthetic auxins and their uses a. Fruit retention b. Herbicides (2,4-D) • Agent Orange

  4. B. Gibberellins 1. Discovery of "foolish seedling" disease 2. Effects of gibberellins a. Increase stem growth b. Breaking of dormancy of buds and seeds

  5. C. Cytokinins 1. Discovery of enhancement of cell division 2. Stimulants to cell division called "cytokinins" 3. Found in meristems and developing tissues, e.g., young fruit 4. Effects of cytokinins a. Enlarging of cells b. Differentiation of tissues c. Development of chloroplasts d. Stimulation of cotyledon growth e. Delay of aging in leaves

  6. D. Abscisic Acid (ABA) 1. Discovery (1963) 2. Location in the plant a. Synthesized in plastids from carotenoid pigments b. Common in fleshy fruits 1) Prevents seeds from germinating while still on the plant 2) ABA inhibits cell growth 3. Other effects of ABA a. Induces bud dormancy b. Regulates stomatal opening

  7. E. Ethylene 1. Discovery (1934) 2. Produced by fruits, flowers, seeds, leaves, roots 3. Hastens ripening of fruits

  8. F. Other Hormones or Related Compounds 1. Oligosaccharins a. Influence cell differentiation, reproduction and growth b. Released from cell walls 2. Brassosteroids a. Have gibberellinlike effect on stem elongation b. Found in legumes and several other plants 3. Batasins a. Promote dormancy in bulbils b. Produced in axillary buds of lilies

  9. III. Hormonal Interactions A. Apical Dominance 1. Defined • suppression of the growth of lateral or axillary buds 2. Auxin and/or cytokinin mediated B. Senescence 1. Defined • breakdown of cell components and membranes that leads to cell death 2. Why do plant parts senesce? C. Other Interactions

  10. IV. Plant Movements A. Growth Movements 1. Movements resulting primarily from internal stimuli a. Helical (Spiraling) movements b. Nodding movements c. Twining movements d. Contractile movements e. Nastic movements 2. Movements resulting from external stimuli a. Phototropism b. Gravitropism c. Other tropisms

  11. B. Turgor Movements 1. "Sleep" movements (Circadian Rhythms) 2. Water conservation movements 3. Contact movements

  12. C. Taxes (Taxic Movements) 1. Defined a. Type of movement that involves either the entire plant or its reproductive cells b. Does not occur in flowering plants 2. Types a. Chemotaxis b. Phototaxis D. Miscellaneous Movements 1. Gliding movements 2. Dehydration movements 3. Explosive movements

  13. V. Photoperiodism A. Discovery B. Critical Day-length 1. Short-day plants 2. Long-day plants 3. Intermediate-day plants 4. Day-neutral plants

  14. VI. Phytochrome A. Characteristics and Location in Plant B. Phytochrome Interconversions • Pred (Pr) and Pfar-red (Pfr) C. Functions of Phytochrome

  15. VII. A Flowering Hormone? A. Defined • hypothetical hormone that induces flowering in plants B. Chailakhyan's Experiments with Flowering

  16. VIII. Temperature and Growth A. Optimum Temperature B. Thermoperiodism

  17. IX. Dormancy and Quiescence A. Definition of Terms 1. Dormancy 2. Quiescence B. Breaking of Dormancy 1. After-ripening 2. Stratification

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